In the past, sheets with glue pre-applied thereto such as disclosed in my co-pending U.S. patent application Ser. No. 06/453,814, filed Dec. 27, 1982, have been used successfully; however, these increased the thickness of the bound-together glued portion and occasionally the binding of adjacent sheets has not been as effective as may be desired. The present invention is intended to cure both of these problems by providing an indented recess portion with heat-responsive glue applied therein and providing openings through the indented portion to expose the glue on the opposite side of the sheet from the indentation to permit glue-to-glue binding when pressurized heat is applied to the sheets to be bound.